1. Technical Field
The present invention relates to a recording apparatus that is provided with ribs for guiding a recording target medium to the downstream side.
2. Related Art
A recording apparatus such as a facsimile or a printer, especially, an ink-jet printer, includes a guiding member (also called as platen) provided at a position where it faces a recording head. The guiding member is provided with a plurality of ribs for guiding the recording target medium to the downstream side. The ribs are formed at predetermined regular intervals in the direction orthogonal to the direction along which a recording target medium such as recording paper is transported. The ribs have a function of forming regular ups and downs (cockling) in paper that gets swollen as it absorbs ink, thereby avoiding serious irregularity in the distance between the paper and a recording head (hereinafter referred to as “paper gap”) (for example, refer to JP-A-2005-212205 and JP-A-2005-262832).
In some recording apparatuses, ribs for guiding (supporting) paper are separately arranged as upstream ribs and downstream ribs. The reason why they are separately arranged is as follows. For example, let us consider that a recording apparatus has the following structure; an optical sensor is provided on a carriage, on which a recording head is mounted, so as to detect the width of paper by optical sensing as disclosed in JP-A-2005-212205 and JP-A-2005-262832; if the ribs are formed at positions where they face the optical sensor, the problem of false detection will arise. To avoid false detection, the ribs are split at the position facing the optical sensor in the recording apparatus disclosed in JP-A-2005-212205 and JP-A-2005-262832.
When an ink-jet printer that can perform so-called borderless printing, which is a technique that utilizes the entire sheet of paper for a printout while leaving no white spaces around the edges, is used, it is necessary to eject ink onto not only an area inside the leading edge and the rear edge of paper but also areas outside these edges for such printing. For this reason, ribs are separately arranged for leaving a space of a cavity into which ink is to be discarded. That is, the ribs are separately arranged as upstream ribs and downstream ribs so as to form the ink-discarding cavity.
In some cases, in order to prevent the rising of paper from ribs, the paper is transported while being pressed against the ribs by means of a transportation roller. When a resin material is used as the material of the guiding member that is provided with the ribs described above for cost reduction or any other reason, there is a risk that the ribs might wear due to the pressing of paper against the ribs, which causes problems resulting from the wear (e.g., a change in a paper gap or the position/attitude, etc. of paper).
On the other hand, in sensing by means of an optical sensor, an optical reflectance difference between paper and an area outside the paper has to be large; the use of a metal material for the purpose of preventing the wear of ribs should be avoided. The reflection factor of a metal material is high. A metal material requires after-treatment such as coating. In addition, it is difficult to obtain a proper optical reflectance difference after the coating has come off. For these reasons, the use of a metal material should be avoided.